Yesterday SpaceX succeeded in the first Falcon Heavy launch, but the payload, a Tesla car has no real useful purpose (except for company prestige).

Thus, can it be considered as space junk ? How long will the car stay in orbit and has it been designed for an atmospheric disintegration? Is the car equipped with a propulsion system to change its trajectory in case of imminent collision risk ?

$\begingroup$Based on the answers you've gotten, this largely depends on the definition of "Space Junk" that you're using - it might help to indicate what definition you are using, so that answers can be written accordingly.$\endgroup$
– ZibbobzFeb 7 '18 at 17:48

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$\begingroup$There's no legal definition for space junk. The 2010 UN Space Debris Mitigation Guidelines define space debris as “all man-made objects, including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional.” Since the Falcon Heavy payload is not in Earth orbit, it is not space debris as defined in that document. But there are other definitions. Consider rephrasing the question in a way that can be answered, not just argued over.$\endgroup$
– David MolesFeb 7 '18 at 18:05

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$\begingroup$Shouldn't this be closed as opinion-based? It looks like we're just arguing about the definition of "junk" here.$\endgroup$
– user2357112Feb 7 '18 at 21:14

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$\begingroup$@user2357112: Competent answers will provide and support a definition of "junk" that does not rely on opinions. The top-voted answer, for example, relies on fairly straightforward arguing from NASA standards and known statistics. So it's not POB, as there's something other than opinions to appeal to.$\endgroup$
– Nathan TuggyFeb 10 '18 at 19:54

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No, because it is not in Earth orbit

First the payload does have a purpose: it is a boilerplate, and those have a purpose, namely to "test various configurations and basic size, load, and handling characteristics of rocket launch vehicles".

Second, you are asking...

is the car equipped with a propulsion system to change its trajectory in case of imminent collision risk ?

No, it is not. The payload is not in Earth orbit any more. It is in an elliptical heliocentric orbit. The likelihood that is will ever be a collision risk for anyone or anything is infinitesimal.

Generally — as this NASA page states — we only consider objects in Earth orbit to possibly be space junk, or "orbital debris" as the more technical term for such things are.

1). What are orbital debris?

Orbital debris are all man-made objects in orbit about the Earth which no longer serve a useful purpose.

The reason only objects in Earth orbit are considered "orbital debris" is because only those are of relevance to us. We do not expect to ever run into man-made objects that are not in Earth orbit, simply because the probability of a collision is so small and the number of them is so low, that combined it is not worth the effort to try to prevent any such collisions. By comparison we do not even try to protect against meteor/meteorite strikes even though the Earth is hit by such — the size of the Roadster or larger — several times each year. If that does not bother us enough to warrant taking measures to prevent it from happening, why would the Roadster warrant it? It simply does not.

If you personally want to call the Roadster "space junk" you may do that of course, but I will counter that by saying "Yeah but it is harmless space junk".

$\begingroup$The number of rocks of equivalent size that orbits the Sun could not be estimated, about 65000 objects within the asteroid belt are known. But rocks of the size of a car could not be detected from Earth.$\endgroup$
– UweFeb 7 '18 at 13:36

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$\begingroup$Space junk is anything that we put up there that we're not using, regardless of whether it's in earth orbit.$\endgroup$
– TristanFeb 7 '18 at 14:39

$\begingroup$The location matters. We worry about junk in Earth orbit because there's a much higher (relative) chance of hitting it, as opposed to junk orbiting the sun (a MUCH larger obit)$\endgroup$
– AlexanderFeb 7 '18 at 23:45

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$\begingroup$@Tristan Thank you. Point 1 on that page (emphasis mine): 1). What are orbital debris? Orbital debris are all man-made objects in orbit about the Earth which no longer serve a useful purpose.".$\endgroup$
– MichaelKFeb 8 '18 at 15:20

Yes, it's space junk: after about 6 hours, the second stage will stop working and there will be no way to change the trajectory of stage and payload. So it's a non-functional satellite, i.e. junk. An object whose course cannot be controlled, and a potential future navigation hazard.

It's not in Earth orbit, so it's unlikely to cause a problem here. There is no propulsion system that will work after about 6 hours, and no sensors to detect an imminent collision.

If it reenters at some point (because its orbit intersects that of Earth), reentry will be fast enough that it'll burn up. If it entered Mars' atmosphere, it might survive reentry and crash on the surface.

$\begingroup$"So it's a non-functional satellite" Is it non-functional? Sure it has no means of propulsion, but it was never designed to. Instead, it was designed to fly around for an indefinite period of time as a testament to Tesla, SpaceX, and Sci-fi culture... or in simple terms Art. Could this not be considered a function?$\endgroup$
– NPSF3000Feb 8 '18 at 3:39

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$\begingroup$It can be noted that a car is much safer than a block of concrete in case of reentry. Aerodinamic as it may be, it will be torn appart and burn.$\endgroup$
– MadlozozFeb 8 '18 at 8:48

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$\begingroup$The car also has a data payload, containing works of art and culture. Therefore I don't think it should be considered "junk". Will the Voyager probes be considered "Junk" once their power source decays beyond use? They contain plaques which were designed to be read by extra-terrestrial species, so it doesn't require power. The Tesla data-payload can be considered the same$\endgroup$
– JLoFeb 8 '18 at 16:53

${}^1$ That the term "Space Junk" (as used in this answer and which is probably the right answer) has a different generally agreed meaning in spacecraft lingo than just plain "Junk" has been pointed out in this answer as well as in in this comment.

2. It is not "junk${}^1$".

Will Voyagers, with their plaques and records that Carl Sagan and a host of others word so hard to make happen be simply "space junk" when we loose contact? Will New Horizons, carrying Clyde Tombaugh's ashes and artifacts be junk as well? Are you sure? Perhaps consider the points made in this answer. "One person's junk is another person's treasure..."

The Pioneer Plaque, junk as well? Or is there in fact still a purpose to these spacecraft's existence?

The spacecraft also serves as a symbol. It has a purpose, people will visit it again in the future if it hasn't collided with something, there's absolutely no question about that. There are already plans to revisit the Apollo landing sites.

It is a statement, a symbol, an artifact. It's more than discarded rocket body number n, it's a red sports car in space!

$\begingroup$Being art does not exclude it from being junk. www.visual-arts-cork.com/definitions/junk-art.htm$\endgroup$
– ZibbobzFeb 7 '18 at 14:51

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$\begingroup$Art is very subjective. And still, it can be both.$\endgroup$
– PolygnomeFeb 7 '18 at 15:18

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$\begingroup$Plus, I consider things like the Apollo 12 S-IVB space junk, but still also consider it of great historical importance and of cultural value. One does not necessarily exclude the other. Junk is "old or discarded articles that are considered useless or of little value." Note the "or". The car is certainly discarded and useless, as is the aforementioned S-IVB. Which is enough to qualify it as junk, it does not have to also fulfill the condition of being value-less.$\endgroup$
– PolygnomeFeb 7 '18 at 15:21

It depends.

In the industry, the concern with space junk is whether or not certain objects are a navigational hazard. If the Falcon Heavy payload were on a collision course with an active spacecraft, then it would definitely be a navigational hazard, as it has no way to redirect itself. That said, there really isn't a lot to avoid out where it is going.

As can be seen in the other answers, the issue of whether or not the payload can be considered "defunct" is more subjective, and in fact it is an issue that is unlikely to be resolved by some formal definition. Space junk is loosely defined for a reason. We talk about it from a collective perspective. Individual items simply aren't relevant until they are an active threat. That isn't to say that individual items aren't tracked--they are. That is part of the mitigation strategy for the broader issue.

If you define "space junk" as any human artifact anywhere in space serving no useful purpose, then Starman has become space junk, but so have a number of NASA or other space agency probes that have either malfunctioned, or exhausted their propellants and/or power supplies (RTGs), so the Voyagers are destined to become "space junk" in interstellar space.

If you define "space junk" as a synonym for "orbital debris" (human artifacts in Earth orbit serving no useful purpose, as is usually the case), then no, Starman is not because it is not in Earth orbit.

Junk in space only matters if

It has the potential to collide with or crash down upon something that matters to you

It could introduce some form of contamination into a target of scientific study e.g. microbes on Mars.

It's still transmitting imagery, so by that standard it's not junk (yet). Once the batteries drain it will be inert. It has no propulsion capability to speak of, not even reaction control thrusters to change attitude.

It's on an orbit where aphelion will be in the asteroid belt; the odds of it posing a hazard to future space flight is low. If, in the coming years, it encounters Earth and re-enters, it will burn up fairly easily.

Thank you for your interest in this question.
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